1. Field of the Invention
The present invention relates to a magnetic lifting apparatus and more particularly to an improved magnetic lifting apparatus by using neodymium magnet, which prevents the neodymium magnet from being oxidized to improve magnetic performance and endurance with switchable function of an on/off handle.
2. Description of the Related Art
The magnetic lifting apparatus is used in the art for lifting, conveying and releasing the ferromagnetic objects by magnetizing on or off switching.
Generally, the magnetic lifting apparatus comprises poleplates, interval members' therebetween, side walls and a top cover on which a hook is disposed. The plate-shaped poleplates are provided with a permanent magnet arrangement sandwiched in between. Each pair of poleplates is separated by a non-magnetic medium. A rotor is disposed to switch magnetic polarity by using the switching handle.
In the center of the rotor, there is an axial aperture through which the axle is rotatably inserted to the rotor and the polarity plates. One end of the axle is connected to the switching handle for rotation of the axle.
Depending on on/off position of the switch handle, the objects are lifted or released. In the lifted state of the objects, there is provided a locking member for preventing the rotor from unintentionally moving to the off direction.
In rotating the switch handle, the polarity of the line of magnetic force is changed as the directional position of permanent magnetic is switched. The magnetic force becomes OFF in case that the line of magnetic force is applied to the opposite poleplates divided by the non-magnetic medium. If the rotor is switched again, the direction of the line of magnetic force is applied to the poleplates, thereby adsorbing the objects under the poleplates with a strong magnetic attraction to lift and move to the desired place.
For a permanent magnetic of the magnetic lifting apparatus, the ferrite magnetic is widely used, having the remaining magnetic density under 2,000 gauss.
In order to improve, however, a relatively large size of the ferrite magnetic is required to improve magnetic attractive performance.
The large size of the ferrite magnetic necessitates a relatively large size of the magnetic lifting body in a magnetic lifting apparatus, which is disadvantageous to use and in view of the high manufacturing costs as well.
Use of the neodymium magnet in the range of the remaining magnetic density of 10,000-13,000 gauss may improve function of the magnetic body. However, the neodymium magnet has a fatal disadvantage of easy oxidation when the neodymium magnet is exposed in atmosphere, thereby lowering magnetization.
In order to prevent the above disadvantage, coating on the surface of the neodymium magnet with resin or metal may be suggested. However, use of the coated neodymium magnet in the rotor results in exfoliation of the coated film because it is inevitable to rotate in contact with the poleplates.